With increasing smartphone sales and consumption of bandwidth, wireless providers and device manufacturers are being pressured to improve spectral efficiency. Multi-band smartphones can use multiple channel filters to effectively use the wireless spectrum. The prospect of ever rising cost, complexity and space requirements in smartphones has driven the search for an ultra-wideband tunable filter. To date, research has focused on microelectromechanical systems (MEMS) or other switched filter banks and on tunable capacitors, but these solutions have not yet met all the criteria for commercial success. Without a cost-effective ultra-wideband tuning technology free of distortion, utilization of spectrum will be inadequate, adversely affecting consumers, industry and the economy.
Accordingly, there exists a need for a cost-effective ultra-wideband tuning technology with low distortion, and particularly for tunable filters, cancellers, and duplexers.